1. Field of the Invention
The present invention relates to an ink jet recording apparatus for recording by discharging ink from recording means mounted on a carriage to a recording medium.
2. Related Background Art
The recording apparatus, which is provided with such function as a printer, a copying machine, a facsimile, or the recording apparatus, which is used as an output device for a complex electronic apparatus that includes a computer, a word processor, or a work station, among some others, is the one that records images (including characters, symbols, and the like) on a recording medium (a recording material) such as paper, cloth, plastic sheet, or OHP sheet.
On these apparatuses, an ink jet type recording apparatus (an ink jet recording apparatus) performs recording by discharging ink from recording means (a recording head) to a recording medium, which facilitates making recording means compact, and also, makes it possible to record images in high precision at high speed on an ordinary paper sheet without any particular treatment given thereto. There are also advantages, among some others, that its running cost is lower; being of non-impact type, it can operate with a lesser amount of noises; and by use of many kinds of ink (color ink, for instance) it can record color images with ease.
As the energy generating element for generating energy utilized for discharging ink from the discharge ports of an ink jet recording head, there is the one that uses electromechanical converting elements, such as piezo elements; the one that discharges ink droplets by the activation of heat generated by the irradiation of electromagnetic waves, such as laser; or the one that heats liquid by use of electrothermal converting elements each provided with heat generating resistive device. Of these means, the ink jet type recording means (the recording head), which discharges ink as ink droplets by the utilization of thermal energy, makes it possible to arrange discharge ports in high density for recording in high resolution. Particularly, among them, the recording head that uses electrothermal converting elements as energy generating devices makes it easier to miniaturize the head, and also, makes it possible to fully utilize the advantages of the IC technologies and micromachining techniques, which have shown remarkable progress of art and reliability in the semiconductor field in recent years. A recording head of the kind has, therefore, an advantage, among many others, that a highly precise assembling is possible with ease at lower costs of manufacture.
Meanwhile, there are various demands as to the materials of recording medium to be used. In recent years, developments have been made to meet these demands. Then, the recording apparatus is now made capable of using such recording medium as cloth, leather, non-woven fabric, or each metal, besides paper (including thin paper sheet, processed sheet) or thin resin plate (OHP or the like).
For the ink jet recording apparatus of serial type where recording is made with the main scanning in the direction orthogonal to the carrying direction of a recording sheet (recording medium), images (including characters, symbols, and the like) are recorded by the recording head which is mounted on a carriage to travel along the recording sheet after the recording sheet has been set at the predetermined recording position, as well as by the execution of sheet feeding in a predetermined amount (sub-scanning), hence forming images on the recording medium. FIG. 20 is a perspective view which shows the conventional example of an ink jet recording apparatus that forms images by use of recording means that scans on a recording medium relatively. In FIG. 20, a reference numeral 101 designates recording means (a recording head) which performs recording by discharging ink; 102, the carriage mounting the recording head thereon, which travels in the direction at right angles to the sheet feeding direction (carrying direction) of the recording medium (recording sheet); and 103 and 104, the guide shaft and auxiliary rail, which support the reciprocation of the carriage 102.
In FIG. 20, a reference numeral 105 designates a carriage motor for driving the carriage; 106, a driving pulley direction connected with the carriage motor; 107, an idler pulley arranged to face the driving pulley 106; 108, a timing belt tensioned around the driving pulley 106 and the idler pulley 107 to transmit the driving power of the carriage motor 105 to the carriage 102; 109, a carrying motor (sheet feeding motor) for carrying (feeding) a recording sheet 110; 111, a cap to protect the discharge port surface of the recording head 101 from being dried at the time of non-recording; 112, a carrier roller for carrying (feeding) the recording sheet 110; and 113, a pre-discharge receptacle for receiving ink (pre-discharge ink or the like) discharged from the recording head 101 for the other operations than recording, which is positioned between the cap 111 and the recording sheet 110.
In FIG. 20, there is arranged a pressure roller 114 for providing the carrying power for the recording sheet 110 by pressing it to the carrying roller 112 by use of biasing means which is not shown. Then, in the vicinity of the aforesaid pre-discharge receptacle 113, a wiping member (not shown) is arranged to wipe off ink or the like adhering to the discharge port surface, which may impede appropriate ink discharges. This wiping member is usually formed by an elastic plate member such as rubber. Also, a double-arrow mark 115 indicates the directions in which the carriage 102 reciprocates (main scanning direction), and an arrow mark 116 indicates the rotational direction of the carrying roller 112 at the time of recording.
The operation of the ink jet recording apparatus shown in FIG. 20 is as follows: when a recording operation begins, the cap 111, which is closely in contact with the recording head for protecting the discharge ports of the recording head 101, is separated from the recording head. Then, the driving power of the carriage motor 105 is transmitted to the carriage 102 through the timing belt 108 tensioned around the driving pulley 106 and the idler pulley 107. In this manner, the traveling direction and position of the carriage 102 are controlled.
The recording head 101 travels above the surface of the recording sheet 110 together with the carriage 102 in a predetermined distance, and then, reverses the traveling direction towards the cap 111 (toward the original capping position). This operation is repeated to perform reciprocation in the directions indicated by the double-arrow mark 115. In synchronism with this traveling of carriage 102, the recording head 101 is driven in accordance with recording information. Ink droplets are discharged (to fly and adhere) to specific positions on the recording sheet 110 for recording images per one-line portion continuously. The recording sheet 110 is carried in a predetermined length by rotating the carrying roller 112 in a predetermined amount in the direction indicated by an arrow 116 by use of the sheet feeding motor 109 per completion of main scanning of recording head 101. By repeating these operations, recording is performed for the recording sheet 110.
The pre-discharge receptacle 113 is arranged at a position outside the predetermined position (recording area) of the recording sheet 110, which is between the cap 111 and the recording sheet 110, for-example. As a result, in order to execute pre-discharge, the recording head 101 should move to the position of the pre-discharge receptacle 113 by means of the main scanning of the carriage 102. Then the pre-discharge should be executed in a state where the recording head is stationary at the position of the pre-discharge receptacle 113. Here, it may be possible to use the aforesaid cap 111 in place of the pre-discharge receptacle 113.
Also, in order to maintain the normal recording operation, there is a need for wiping off ink, ink mist, or other dust particles adhering to the discharge port surface of the recording head 101 per passage of predetermined time or at a timing subsequent to having executed pre-discharge or the like. Therefore, a wiping member (not shown) is provided for wiping off to clean the discharge port surface of the recording head 101. Usually, the wiping operation is executed about once per one recording sheet.
FIG. 21 is a vertically sectional view which schematically shows the state where the cap 111 is closely in contact with the discharge port surface 117 of the recording head 101. In FIG. 21, the cap 111 is formed by an elastic material such as rubber, and the circumferential portion 118 thereof is in the form of ribs. Thus, when pressed to the discharge port surface 117, the rib portions are compressed to be elastically deformed only to the height designated by a reference numeral 119 so that the cap is in contact (closely) with the discharge port surface 117 without a gap. Also, the cap 111 is connected with a recovery system (suction pump and others) which is not shown and a waste ink absorbent through the tube 121 which is connected with through hole 120 arranged for the backside of the cap.
When the carriage 102 and the recording head 101 are at the home position, the cap 111 is pressed to be closely in contact with the discharge port surface 117 by use of a driving mechanism (not shown) comprising a recovery motor, a plurality of gears, and a magnetic clutch, thus eliminating the defective ink discharges that may be brought about by the dried ink or coagulated ink on the ink discharge unit or protecting the discharge port surface 117.
Also, in this state (of being capped), the air in the tube 121 is sucked in the direction indicated by an arrow 122 by driving a tube pump which is not shown. Then ink in the recording head 101 is sucked (sucked out) through the cap 111 and the tube 121, and at the same time, ink is replenished afresh from an ink tank into the recording head 101. In this manner, bubbles and overly viscous ink in the recording head 101 are removed. After the recovery process of the recording head 101 has been completed, the cap 111 is allowed to part from the discharge port surface 117 by means of the aforesaid driving mechanism, hence making it possible to shift the carriage 102 and the recording head 101 in the main scanning direction (the direction perpendicular to the surface of FIG. 21) to initiate recording operation.
In recent years, portability is also required for a recording apparatus, such as a printer. For a note type small printer, in particular, it has been demanded increasingly more to make the printer lighter and smaller. However, for the conventional ink jet recording apparatus as described above, the cap 111, the pre-discharge receptacle 113, and others required for the formation of the recovery system are all arranged outside the recording area as shown in FIG. 20. Further, then, the dimension of the apparatus main body in the traveling direction of carriage is substantially determined by the width of a recording sheet plus that of the recovery system. Therefore, in order to reduce the widthwise dimension of the recording apparatus in the carriage traveling direction, it is required to make the recovery system itself smaller (that is, the constituents of the recovery system should be curtailed and miniaturized). However, there is automatically a limit to making the recovery system itself smaller, and it has been almost impossible to attempt the reduction of the widthwise dimension thereof. For a method of solving a problem of the kind, a proposal has been made as disclosed in Japanese Patent Application Laid-Open No. 9-11502 that a carriage and a recovery system are integrally formed as one body, and driven in the main scanning direction. With this method, however, load to the carriage motor becomes greater to the extent that the recovery system and the carriage are integrally formed or there is a drawback that the dead space becomes greater due to the integral structure thereof.
In consideration of the problems encountered in the conventional art as discussed above, the present invention is designed. It is an object of the invention to provide an ink jet recording apparatus for which the dimension of the apparatus main body in the carriage traveling direction is made significantly smaller neither inviting the increase of load given to the carriage motor dead space nor inviting the increase of the dead space irrespective of the size of the recovery system.
It is another object of the invention to provide an ink jet recording apparatus provided with control means for optimizing the relative movements of the recording head installation unit and recovery means, and the conveyance of a recording medium as well.